Properties of Water. WATER MOLECULES ARE MADE OF 2 HYDROGEN ATOMS AND 1 OXYGEN ATOM. THE HYDROGEN...
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Transcript of Properties of Water. WATER MOLECULES ARE MADE OF 2 HYDROGEN ATOMS AND 1 OXYGEN ATOM. THE HYDROGEN...
Properties of Water
• WATER MOLECULES ARE MADE OF 2 HYDROGEN ATOMS AND 1 OXYGEN ATOM.
• THE HYDROGEN ATOM OF 1 MOLECULE I S AT TRACTED TO THE OXYGEN ATOM OF ANOTHER MOLECULE – HYDROGEN B ONDING
The Structure of Water
Specific Heat of Water
Because of the hydrogen bonding of water, it has a high specific heat This means that
it can hold a lot of heat
It heats and cools slowly
Specific Heat
The amount of heat required to change the temperature of 1g of a substance by 1 degree celcius.
In other words, the amount of heat required to change the temperature of a substance
Higher specific heat means it’s harder to warm something up.
Water Density & Temperature
• Water is most dense at 4oC (39oF) when atoms are closest to each other
• Atoms spread out when forming ice and vapor
The Structure of Ice
The Structure of Water (Liquid)
The Structure of Water Vapor
Water Density in the Ocean
• Ocean water temperatures range from -2oC to 30oC (28oF-86oF)
• In the ocean, the densest water is at the bottom and the least dense is at the top
Lowest Density
Highest Density
Mixed Layer
Surface Zone: 2% of ocean water is found in the surface
zone Lowest density, lowest salinity and highest
water temperatures
Transition Zone: 18% of ocean water is found in the
transition zone The layer is in between the warmer surface
zone and the colder deep zone The thermocline and pycnocline are located
in the transition zone
Deep Zone: 80% of ocean water found in the deep zone Sunlight never reaches the deep zone Water temperature is only a few degrees above freezing Highest density, highest salinity, lowest
temperatures
Three Ocean Layers:
Deep Currents: Water Density and Salinity
• 3-5% of ocean water is salt – known as salinity
• The greater the salt content, the denser the water is
• The ocean water is layered with the greatest amount of salinity at the bottom – halocline
• Most ocean salt comes from weathered rocks on the land
Changes in Salinity
The salinity of ocean water can be increased by removing surface water Evaporation Ice/Glacier Formation
The salinity of ocean water can be decreased by adding surface water Precipitation Melting of Ice/Glaciers Water Runoff from Land
Thermohaline Current
• Changes in the density of water results in a worldwide circulation of water
• Density differences are created by changes in temperatures and salinity levels
Water is heated at the Equator by the Sun and spreads outward towards the Polar Regions by the wind
• Water is cooled in the Polar Regions, increasing the density, then sinking to the bottom of the ocean – Downwelling
• Water spreads outward (towards the Equator) on the bottom of the ocean floor
Creation of the Thermohaline Current
Thermal Expansion - objects expand when heated
Continuation of Water Movement
Surface winds push the coastal water outwards to the ocean, pulling water up from the ocean floor - upwelling
Heat Exchange from the Thermohaline Current
• The Polar Regions are warmed by the warm currents
• Releases heat into the atmosphere as the water cools
• Helps increase the temperature as much as 41oF
• The Equator is cooled by the cool currents
• The cold currents absorb heat from the atmosphere
• Helps cool the Equator by as much as 30oF
• CIRCULAR MOVEMENT OCEAN CURRENTS
• CREATED BY WIND AND EARTH’S ROTATION
• SPINNING RESULTS FROM THE CORIOLIS EFFECT
Ocean Surface CurrentsWhat is an Ocean Gyre?
Coriolis Effect
• The spinning of Earth causes objects to move in a curved line across Earth’s surface
• This movement causes the gyres to move clockwise in the Northern Hemisphere and counter-clockwise in the Southern Hemisphere
https://www.youtube.com/watch?v=i2mec3vgeaI
North Atlantic Gyre
Each gyre is made up of several smaller surface currents
North Atlantic Gyre: Gulf Stream Current North Atlantic Current Canary Current North Equatorial Current
Characteristics: Western Stream (Gulf
Stream Current) – warm, narrow, deep, fast-moving
Eastern Stream (Canary Current) – cold, wide, shallow, slow-moving
Gulf Stream Curren
t
N. Atlantic Current Canary
Current
N. Equatorial
Current
Influence of the Wind
The currents that form the gyres following the direction of the wind Easterlies – move
the Gulf Stream Current northeast towards Northern Europe
Westerlies – move the Canary Current southwest towards South America and Mexico
Effects of Global Warming• Surface warming
of the water and increased freshwater (melting glaciers)
• Reduces downwelling
• No surface cooling
• Reduction of water circulation (loss of 20-50% of the water movement)
Impacts of Weakening Thermohaline Current
• Europe will experience a cooling trend (“The Big Freeze” last happened 12,800 and 11,500 years ago)
• Glacial tundra in Scandinavia
• Increased glaciation in mountain ranges worldwide
• More dust in the atmosphere from deserts in Asia
• Drought worldwide
• Cooling of Western North America and South America
• Extinction of many species
Weakening of the North Atlantic Currents
The ocean circulation of the Gulf Stream Current has been reduced by 30% in 2005
The North Atlantic Current & Norway Current has basically stopped in 2010
These currents work to: keep Ireland and the United
Kingdom mostly ice free the Scandinavia countries from
being too cold the entire world from entering
into another Ice Age
Normal Current Movement
Current Movement – August 2010
Coastal vs. inland climate
Because water has a high specific heat, its temperature will undergo very little changes. Thus, coastal areas close to the ocean tend to have moderate temperatures with a low variation in temperature. Areas further inland will be farther from the ocean and will thus experience larger variations in temperature.
Surface Currents vs. Density Currents
Surface Currents:
Movement in ocean caused by wind
Moves horizontallyIs on ocean surface
Density Currents:
Movement in ocean caused by differential salinity and temperatures of water
Moves vertically, relative to the surface currents
Involves upwelling and downwelling
Horizontal movement: Surface currentsDensity differences, sunlight, and wind cause currents
Ocean currents play a major role in maintaining Earth’s heat balance:• Heat is transferred from the tropics (near the
equator) where there is excess heat, to the polar region where there is less heat
Vertical movement: Density currents
Upwelling – water rich in nutrients from the bottom rises (excellent for fisheries!)
Downwelling – water rich in dissolved gases sinks (brings O2 to deep-water life!)